Deputies responding to a report of an assault in the 1900 block of Hidden Crest Drive shortly after 5 p.m. Sunday found 63-year-old Martha Margain-Velarde suffering from severe injuries, according to sheriff's officials. Medics took her to a hospital, where she was pronounced dead.
Before fleeing, the suspected assailant also allegedly attacked and seriously injured his 37-year-old brother, who was able to escape and make an emergency call, homicide Lt. John Maryon said.
Detectives tracked down Erik Enrique Margain in the 1500 block of Gustavo Street, about a half-mile north of the site of the assaults, and arrested him on suspicion of murder and attempted murder.
Authorities have released no suspected motive for the assaults.
Margain was being held without bail at San Diego Central Jail pending arraignment, scheduled for Wednesday afternoon.